of certain species of Wfllow. — Part 2n>7. 



259 



very large numbers of S. cordata, the species on which S. pomum is 

 normally found. This gall is evidently allied to those produced by the 

 European Niematus intercus and X. gallarum, which are described as 

 "globose, spongy, pedunculated galls along the mainrib of the leaf;" 

 i Westw. Jut ro<l. IT, p. 105;) but it differs in growing, not exclusively 

 from the mainrib, hut indiscriminately from any of the veins. Distinct 

 from 8. pomum by its being peduncled not sessile, and by its smaller 

 size and the general absence of a rosy cheek, and from S. desmodioidcs 

 by its short peduncle and by its very different shape. 



Larva. The larva on August 25 was apparently 18-footed, with true legs, 

 ]2 abdominal prolegs on joints 5 — 10, but no anal prolega that I could discover. 

 When at rest, it elevated its entire abdomen behind the true legs in the air. as 

 I notice to be the case, but only in the earlier stages of its life, with a 20-footed 

 larva feeding on the leaves of Salix nigra Aug. 28. from which larva two weeks 

 subsequently I bred six males and eighteen females of an undescribed Messa ; 

 and as is said to be also the habit of the 20-footed external-feeding larva of the 

 European Xcmatus ochraccus, which also lives on the willow; (Westw. Intr. II, 

 p. 104 :) except that in these two cases the larva clasps the leaf with some of its 

 anterior prolegs. The length of the larva, Aug. 25, was .17 — .23 inch, the body 

 being about six times as long as wide. Color whitish hyaline ; head slightly 

 tinged with dusky; mouth dusky; eye-spots circular and black. Anal segment 

 equal in length to two of the others, and apparently divided in two by a trans- 

 verse medial suture. The larva goes underground to transform; for after my 

 first imago appeared, out of about 50 sound, nnshrivelled galls. I found all but 

 .". bored and nothing remaining of them but a shell as thin as papier. And in 

 those three, when subsequently opened, it appeared that the larva had perished 

 when immature. 



Pupa unknown. 



Imago. Nematus s. pisum. n. sp. — 9 Shining greenish-white. Head with 

 the eyes, a quadrate spot enclosing the ocelli, and extending behind on to the 

 disk of the occiput, but not near reaching the antennae in front, and separated 

 from the eyes by a pretty wide orbit, a dot above the origin of each antenna, 

 and also the tips of the mandibles, all black. Clypeus emarginate in a circular 

 arc of about 90°. Labrum rounded at tip. Antennae three-fifths as long as the 

 body, joints 3 — 5 subequal, — 8 slowly shorter and shorter, 9 as long as 8. the 

 scape black, the flagellum brown-black. Thorax, including the basal plates, 

 black, with the tegulseand the entire collare, except a fuscous spot on each low- 

 er angle, all greenish-white. Cenchri whitish. Abdomen entirely black, except 

 the venter, and a more or less distinct pale cloud towards the tip of dorsal joint 

 8; lateral plates black, except the tip of S. Basal membrane whitish. Oviposi- 

 tor concealed ; its sheaths black. Cerci whitish tipped with dusky. Legs pale 

 dish-white, the tarsal tips, especially in the hind legs, and the extreme tips 

 of the bind tibiae, fuscous. Wings hyaline; veins black; stigma fuscous. Length 

 J.ll — .11 inch : front wing J .13 — .17 inch. 



% Differs from J only as follows: — 1st. The quadrate spot on the vertex is 

 only separated from the eye- by a capillary orbit. 2nd. The occiput is black, 

 excepts narrow orbit. 3rd. The antennae are 4-5ths (not 3-5ths) as long as the 

 body, the scape black, the flagellum brown-black above, pale dull green beneath. 



